IO-MAC: A novel hybrid MAC protocol with implicit ordering in WLANs

Contention-based MAC protocols are adaptive to network changes but are inefficient due to frame collisions. On the other hand, reservation-based MAC protocols have advantage of collisions-free transmissions but lack flexibility. In this paper, we propose a novel hybrid contention/reservation-based MAC protocol in WLANs, called IO-MAC, which allows the coexistence of variable reservation period and contention period. According to network dynamics such as stations joining and leaving, changes in traffic types, implicit ordering for collision-free transmissions during reservation period is crated without exclusive control packets. In addition, we design a simple scheme to estimate the number of contending stations, and an adaptive scheme to adjust the length of the contention period to speed up the entrance into the reservation period for contending stations. Simulation results show that the proposed scheme dramatically enhances the network throughput compared to the legacy 802.11 DCF.